Require Last Name entry in a Name field

Our program has a Name field with First Name and Last Name subfields. Some users have decided it is easier to put the first and last names in the First Name field. That causes problems. Is there a way to require an entry in the Last Name subfield?

If you are using a form to enter a new record, you can set a validation rule to prevent the Last Name field to be empty or blank when saving.

@Aprada Thanks for that! I had set the name as a required element on the form, but if I use the Validation Rules on the Last Name subfield, it works!